(1) Field of the Invention
The present invention relates to a method for piercing a double plate for connectin of H-beams and a tool to be used for practising this piercing method.
(2) Description of the Prior Art
In general, as shown in FIG. 1, double plates for H-beams include a relatively long outer flange double plate 111 for connecting two H-beams 101 at left and right flange portions 102 on outer sides thereof, a narrow-width inner flange double plate 113 for connecting the flange portions 102 on inner sides thereof, and a relatively short web double plate 112 for connecting web portions 103 on both the upper and lower sides thereof.
These flange double plates and web double plates have heretofore been pierced and drilled one by one by a boring mill or the like. Accordingly, this processing operation is quite different from the operation of piercing and drilling H-beams 101 to which the double plates are to be attached, and these two operations are conducted separately. According to such conventional technique, the operation of piercing and drilling double plates one by one is very troublesome and it frequently happens that the hole arrangement is deviated among the drilled double plates and between the double plates and the H-beams and it becomes impossible to insert connecting bolts.